When I first moved from Oklahoma to the Puget Sound area, I lived aboard my Catalina 22 from February to June 2005.
I used a 1500 watt heater, and slept in a down sleeping bag on the starboard berth. I couldn't figure out why I was always cold sleeping, even with the heater on and the cabin thermometer reading in the 60s.
Finally, I figured out what was going on. The berth was below the waterline, and the cold from Puget Sound was pulling the heat from me.
I rigged a blanket to cut off the heat loss through the quarterberth and moved up to the V-Berth, which was a couple of inches above the waterline.
I was comfortable for the rest of the winter.
I still can't believe how long it took me to figure that out!
I miss my little boat.
1987 CS 36 Merlin "Kyrie"
"They drove a dump truck full of money up to my house. I'm not made of stone!" -Krusty the Clown